Degraded external display resolution quality via Thunderbolt

External display connected via Thunderbolt suffers severe picture quality degradation compared to connection via HDMI. Compared Macbook Pro M1 vs Macbook Air M3 vs Macbook Pro M4 Max and all of them suffer the same issue with external 4K display connected using Thunderbolt. Resolution is correct but picture quality severely degraded. No issues and superb picture quality with HDMI connection - only on Macbook Pro M4. Is anybody else having same issue?